A boost-less gas turbine engine does not include a boost compressor stage and therefore typically includes a high core pressure ratio (PR) fan which is adapted to compensate for the missing boost stage.
Conventional high core PR fan blades are usually configured with extreme blade turning immediately above the fan hub, which creates a very acute local angle between the blade suction side and the fan hub towards the blade trailing edge. Such an acute angle can help create and/or worsen a corner vortex at the trailing edge of the blade, potentially adversely affecting the quality of airflow at the hub area feeding into downstream blade rows of the compressor, and thereby reducing the overall engine efficiency and stability. Efforts have been made to solve this problem. For example U.S. Pat. No. 6,331,100 teaches providing an S-bowed stacking axis along which centers of gravity of the sections of the blade are aligned, in order to permit the trailing edge to be oriented substantially normal to the root of the bowed suction side and to lean hindward thereabove. U.S. Pat. No. 6,299,412 teaches that the airfoil suction side is laterally or tangentially bowed along the trailing edge near or adjacent the root at the intersection with the disk perimeter in order to increase blade efficiency and improve stall margin.
Nevertheless, there is still a need for improved approaches and solutions to better solve the corner vortex problem.